Even though millions of people were excited to see the eclipse, we quickly learned how dangerous it can be to stare directly at it. You wouldn’t stare directly at the sun without worrying about hurting yourself or damaging your eyesight on a regular day — and that didn’t change just because the moon was in the way.

I used a special pair of glasses to view the eclipse, but I was still anxious afterward that I had done something wrong. I had a little bit of a headache when I came back inside, and I was convinced I had done damage to my eyes. According to Pix 11 New York, this was a common complaint. Ophthalmologist Dr. Steven Couch, who works at Washington University at Barnes-Jewish Hospital, told the news that he’s had lots of patients calling in with headaches, painful eyes, and tiredness after the eclipse. Many people were worried they had inadvertently damaged their eyesight.

I know I had similar worries after watching the eclipse for a few minutes, but Dr. Couch says things like headaches and eye discomfort are probably from staring without blinking for too long. If you want to double check that you didn’t do any damage to your eyes, there’s an easy way: It’s called the Amsler grid.

The Amsler grid is a tool you can use at home to test your eyesight before rushing to the doctor’s office. To test your eyes, cover one up and stare at the dot right in the center of the grid. Do it again with the other eye. According to Pix 11, you should call your eye doctor if any of the lines are missing or become wavy, or if you notice any dark areas, strangely sized boxes, or blurry edges. This test works best if you print out the sheet, which you can download here.

According to All About Vision, the Amsler grid tests your optic nerve. If you stared at the sun for too long, this would be the part of your eye that you would most likely damage. If you look at the sun for too long, you can even burn your retina. The earlier you diagnose these problems, the more likely you and your eye doctor can limit or slow vision loss.